I am working with Illustrator and InDesign ME. Coming from a latin perspective, I want to adjust the "kerning" between characters by extending the line or juncture between letterforms. I see this all the time with Arabic text, but I'm not sure if it is a special font that allows it, or if perhaps there is a glyph in each Arabic font that allows me to extend the line.

So for example, the bismillah normally begins:
بسم
but I would like to extend the line between the "ba" and "sin".
ب--سم

I don't see that in the character set. I am using KFGQPC Uthman Taha Naskh. I realize I won't be able to compete with a calligrapher, but I'm trying to replicate what I'm seeing elsewhere.

Thank you Khaled! This is exactly what I needed. And thank you hhp for the relevant question. I certainly am concerned about usage of it. The pdf Khaled sent helps so much.

Is this behavior generally out of taste and should be avoided unless necessary? Or is it accepted when used minimally? Should I not use it at all if not for justification? And is a tatweel the same as a kashida? I've never been able to do anything with "Kashida" in any of the Adobe apps, and I have assumed I just don't have the right font.

The issue is I need to type a bismillah, but it needs to match the font of the body text, and there is is no full bismillah glyph in the font. (Sometimes I see a nice one in the character map of the font I'm using.) But I don't want to add a tatweel if it is considered tacky. It just looks so strange to see a bismillah so short without the calligrapher's tatweel! (And I got the first message wrong. It's between "sin" and "mim".)

Also, the swashes that you see in latin fonts, are those available in Arabic fonts too? I've never seen them. What I mean is a long extension that curls above or below the line...like in "fi"
في
if the "yah" extended below the baseline for a longer distance without interrupting the other characters. I realize I'm probably getting into "call the calligrapher" domain here. Tasmeem in InDesign is nice, but I just can't afford the nicer fonts yet, and what I have doesn't seem to give enough variation in the line.

Tatweel is an Arabic name of kashida (which I believe is a word of Persian origin, though the word commonly used by Arabic calligraphers as well).

Kashida can be used for many purposes like emphasising, giving room for diacritics in "crowded" situations etc. and when used properly improves the overall appearance of text. Kashida is usually a curvilinear stroke and in traditional fonts too long kasida will look awful when rectangular in shape, yet very few fonts provide curvilinear ones.

For bismillah it is customary to use kashida before the meem, but unless that meem is extended horizontally (unlike most fonts) it will look bad, and I'd not do that my self. Some fonts might include the bismillah ligature ﷽ (U+FDFD) and if present can be a better choice.

As for swashes, some fonts have them with 'swsh' feature, but they are too fancy and shouldn't be used for regular text.

Isn't that part of the "seen" though? I know that in terms of
how glyphs are typically built it would involve a kasheeda,
but maybe the more interesting use of the kasheeda is where
it's not following a long letter (basically a "seen" or "shaa'"),
so in a way it's "optional".

It is important to understand the kashida as an elongation of a letter, and not as something inserted between letters, although most font technologies have tried to implement kashida in terms of an insertion (and most Arabic justification algorithms sadly presume a flat kashida that can be stretched or multiplied without distortion). As an elongation of the letter, the kashida should affect the positioning of disambiguating dots and other marks.

This is an area of Arabic typography that is still very problematic. We can get manually inserted U+0640 kashida to work correctly using OpenType Layout:

But automatic kashida insertion as applied in all justification I've looked at happens after OTL processing, and hence will break display of any non-flat Arabic typeface.

Khaled, I interpret this slightly differently: kashida is an elongation of the first letter but may have an influence on the shape of the second letter because of the way in which the elongation affects the join (or a stylistic influence as in the contextual use of a variant alif in the example I showed above).

Just to provide a little visual to the theory, I'm attaching two images.
The first image shows the font desired and the result of adding one and three tatweelat.
The second image is the Emiri font in InDesign Tasmeem. I'm actually surprised it is so flat.

After looking at this, what is the best option? I do think the tatweel are too flat and not helpful in this context.

When elongating, say, جر, the kashida is hardly part of the jeem as it does not affect it more than it affect the raa (even the placement of the dot does not change), but your view can off course be true in many other cases.

I don't see a real need to use kashida here. It is not a basmala, where the word bism is like a base for the rest of the building.
Anyway, that 1 tatweel example seems to be the best, though it is a tad too "mechanic", it's a straight curve; so tou could make it narrower a bit, probably.

Zuhair, thank you for sharing examples from your font. This is exactly the kind of functionality I wanted. Is the font completed? And does it have multiple weights?

If I understand Aziz and Badr correctly, the tatweelat are incorrect because they do not take into consideration the adjacent letters, yes? This seems to be an inevitable challenge for any Arabic font, unless you are using Tasmeem in InDesign or have a font with an insane number of ligatures. I would like to know if either Aziz or Badr ever use tatweel in other fonts. I know Aziz has been working on his own font(s) with multiple ligatures. Does that mean Aziz only uses his own fonts, never those of others? Or just never tatweelat?

My Naskh font consists of more than 4000 Arabic glyphs. It supports only Arabic language not Persian, Urdu or any other similar language. The tatweel can be inserted at any position in any word up to three levels. So the user will have full control over the tatweel to insert how much tatweel he wants and where he wants. Tatweel works for every character and it will be the user's choice to insert tatweels where he wants, correctly or incorrectly.

As far as the Tasmeem for Indesign is concerned that is a software while it is a font but I have worked hard to make it more powerful and more flexible than Tasmeem and to provide the Arabic users and publishers an easy way to use most of the possibilities of Arabic Calligraphy just by using a font like tatweel up to three levels, alternate shapes of reh and zeh in every word, alternate shapes of Alef, alternate shapes of jeem, alternate shapes for meem, alternate shapes for kaf, swashes for all possible words, alternate shapes for diacritical marks, alternate space between words etc. etc.

For example the word "AR-Rehmaan" in the Basmala. In my font it has 256 or even more possible shapes along with tatweels, swashes, alternate reh and alternate alef etc. I have not counted mark placement in these 256 shapes. Similarly most of the words has several possible shapes.

I hope this font will be one of its own kind, more like a software. Only some kerning work is remaining and I hope that I will complete it very soon Insha-Allah with two weights Regular and Bold.

So far, All typesetting tools built by M$,Adobe+WinSoft are not SMART enough to handle TATWEEL even for their own linear fonts?! They randomly+indiscriminately distribute TATWEEL beautifying some words and spoiling others. So, TATWEEL is virtually useless.

So, think of building a SMART Arabic Font by:
1. Freeing it of any INSANE Kashida.
2. Killing the right side bearings of ALL Glyphs.
3. Adjusting SPACE between 222 + 277 points,
4. Spacing the left side bearings as follows:
_ for Aif + D and their likes = ½ Space Width,
_ for WAW = Zero (0)
_ for R and the likes = Between (-) ¼ + (-) ½ Space Width,then
5. VOLTing R-Kern.

When typesetting, do SWM (Space Width Modulation) as follows:
1. Double the Spaces following the words that end with Aif, WAW + D and the likes,
2. Tripple the Spaces following the words that end with R and the likes>

I think that what we seek here is to get the best of what we can of aesthetic form of Arabic Calligraphy, but must take into account the technical aspects of the aesthetic for the font before you start, including:
= What methods invented by calligraphers to improve the format fonts?
= Kashidas you could put in any place, or a base?

= Calligraphers invented more than one way to increase the beauty of the
font and written texts, including:
- Making different ligatures, some of which extend and some are reduced (ligature alternates).
- Making various alternates of the same character, some of which extend
and some are reduced (character alternates).
- Overlay on top of each letter and gathered together in the form of beautiful (forms).
- The invention of kashidas. :)

= Kashidas is the recent use of it is less beautiful than all of the above, as it is just a plus lengthening between the characters, but to use it must follow certain rules, including:
- May be placed kashidas between certain characters, and may not be between certain characters.
- Kashidas have specific lengths, at least not more than.
- Kashidas affected by the length, the more in length, the greater the concavity and depth.
- Kashidas often affect the preceding character in it, as well as the next character to it.

Zuhair, You did a good job and wonderful, and I wish to continue, but I hope to take into account the technical aspects in addition kashidas, and do not fall in the problems of software that allows everything possible in the font like KALK or TASMEEM; because the average user has no ability to choose artistic combinations correct harmonious with each other.

... do not fall in the problems of software that allows everything possible in the font like KALK or TASMEEM; because the average user has no ability to choose artistic combinations correct harmonious with each other.

+1

One can build a very powerful system but 99% of users will just spoil it with insanely bad choices, so a less powerful system that does The Right Thing™ most of the time is far more beneficial for most common use cases.

Yet, I do not use technical kashidas in my fonts, and rely on methods such as the above-mentioned ligatures and forms of longed letters (Al-Morsalah).
Once, I rely on some artistic additions that change the length of the word, such as the use of various forms of Teethed letters (ب ، ت ، ث ، ن ، يـ ، ئـ), as in the example:

Kashidas - from a technical perspective - need alternatives to a variety of characters preceding and following it; so I whole rules and put it in the form of a table, and then start working.

One can build a very powerful system but 99% of users will just spoil it with insanely bad choices, so a less powerful system that does The Right Thing™ most of the time is far more beneficial for most common use cases.

+

This is what should be in the computer fonts, which work directly on the systems and programs without need to special engine running.